Substituted diketopiperazines and their use as oxytocin antagonists

ABSTRACT

Compounds of formula (1) 
                         
wherein R 1  is 2-indanyl, R 2  is 1-methylpropyl, R 3  is 2-methyl-1,3-oxazol-4-yl and R 4  and R 5  together with the notrogen atom to which they are attached represents morpholino, process for their preparation, pharmaceutical compositions containing them and their use in medicine.

This invention relates to novel diketopiperazine derivatives having apotent and selective antagonist action at the oxytocin receptor, toprocesses for their preparation, pharmaceutical compositions containingthem and to their use in medicine.

The hormone oxytocin is potent contractor of the uterus and is used forthe induction or augmentation of labour. Also the density of uterineoxytocin receptors increases significantly by >100 fold during pregnancyand peaks in labour (pre-term and term).

Pre-term births/labour (between 24 and 37 weeks) causes about 60% ofinfant mortality/morbidity and thus a compound which inhibits theuterine actions of oxytocin e.g. oxytocin antagonists, should be usefulfor the prevention or control of pre-term labour.

International patent application PCT/EP02/14823 describes a class ofdiketopiperazine derivatives which exhibit a particularly useful levelof activity as selective antagonists at the oxytocin receptor. Apreferred class of compounds described therein is represented by theformula A

Such compounds include those wherein inter alia R₁ is 2-indanyl, R₂ isC₃₋₄alkyl, R₃ is a 5 or 6 membered heteroaryl group linked to the restof the molecule via a carbon atom in the ring, R₄ represents the groupNR₅R₆ wherein R₅ and R₆ each represent alkyl e.g. methyl or R₅ and R₆together with the nitrogen atom to which they are attached form a 3 to 7membered saturated heterocyclic ring which heterocycle may contain anadditional heteroatom selected from oxygen.

We have now found a novel group of selective oxytocin receptorantagonists which exhibit a particularly advantageous pharmacokineticprofile.

The present invention thus provides compounds of formula (1)

Wherein R₁ is 2-indanyl, R₂ is 1-methylpropyl, R₃ is2-methyl-1,3-oxazol-4-yl and R₄ and R₅ together with the nitrogen atomto which they are attached represents morpholino.

The group R₂ contains an asymmetric carbon atom and the inventionincludes each enantiomer and mixtures thereof including the racemate.

A preferred compound of the invention is the compound the preparation ofwhich is specifically described in example 1.

The compounds of formula (I) have a high affinity for the oxytocinreceptors on the uterus of rats and humans and this may be determinedusing conventional procedure. For example the affinity for the oxytocinreceptors on the rat uterus may be determined by the procedure ofPettibone et al, Drug Development Research 30. 129-142 (1993). Thecompounds of the invention also exhibit high affinity at the humanrecombinant oxytocin receptor in CHO cells and this may be convenientlydemonstrated using the procedure described by Wyatt et al. Bioorganic &Medicinal Chemistry Letters, 2001 (11) p1301-1305.

The compounds of the invention also exhibit an advantageouspharmacokinetic profile including good bioavailability and low intrinsicclearance when administered by i.v. or p.o. coupled with good stabilityto P450 enzymes including 2C9 and good aqueous solubility.

The compounds of the invention are therefore useful in the treatment orprevention of diseases and/or conditions mediated through the action ofoxytocin. Examples of such diseases and/or conditions include pre-termlabour, dysmenorrhea, endometriosis and benign prostatc hyperplasia.

The compounds may also be useful to delay labour prior to electivecaesarean section or transfer of the patient to a tertiary care centre,treatment of sexual dysfunction, particularly premature ejaculation,obesity, eating disorders, congestive heart failure, arterialhypertension, liver cirrhosis, nephritic or ocular hypertension,obsessive-compulsive disorder and neuropsychiatric disorders. Thecompounds of the invention may also be useful for improving fertilityrates in animals, e.g. farm animals.

The invention therefore provides for the use of a compound of formula(I) for use in therapy and in particular use as medicine forantagonising the effects of oxytocin upon the oxytocin receptor.

The invention also provides for the use of a compound of formula (I) forthe manufacture of a medicament for antagonising the effects of oxytocinon the oxytocin receptor.

According to a further aspect, the invention also provides for a methodfor antagonising the effects of oxytocin upon the oxytocin receptor,comprising administering to a patient in need thereof an antagonisticamount of a compound of formula (I).

It will be appreciated by those skilled in the art that reference hereinto treatment extends to prophylactics as well as the treatment ofestablished diseases or symptoms.

It will further be appreciated that the amount of a compound of theinvention required for use in treatment will vary with the nature of thecondition being treated, the route of administration and the age and thecondition of the patient and will be ultimately at the discretion of theattendant physician. In general however doses employed for adult humantreatment will typically be in the range of 2 to 800 mg per day,dependent upon the route of administration.

Thus for parenteral administration a daily dose will typically be in therange 2 to 50 mg, preferably 5 to 25 mg per day. For oral administrationa daily dose will typically be within the range 10 to 800 mg, e.g. 20 to150 mg per day.

The desired dose may conveniently be presented in a single dose or asdivided doses administered at appropriate intervals, for example as two,three, four or more sub-doses per day.

While it is possible that, for use in therapy, a compound of theinvention may be administered as the raw chemical, it is preferable topresent the active ingredient as a pharmaceutical formulation.

The invention thus further provides a pharmaceutical formulationcomprising a compound of formula (I) together with one or morepharmaceutically acceptable carriers thereof and, optionally, othertherapeutic and/or prophylactic ingredients. The carrier(s) must be‘acceptable’ in the sense of being compatible with the other ingredientsof the formulation and not deleterious to the recipient thereof.

The compositions of the invention include those in a form especiallyformulated for oral, buccal, parenteral, inhalation or insufflation,implant or rectal administration.

Tablets and capsules for oral administration may contain conventionalexcipients such as binding agents, for example, syrup, acacia, gelatin,sorbitol, tragacanth, mucilage of starch or polyvinylpyrrolidone;fillers, for example, lactose, sugar, microcystalline cellulose,maize-starch, calcium phosphate or sorbitol; lubricants, for example,magnesium stearate, stearic acid, talc, polyethylene glycol or silica;disintegrants, for example, potato starch or sodium starch glycollate,or wetting agents such as sodium lauryl sulphate. The tablets may becoated according to methods well known in the art. Oral liquidpreparations may be in the form of, for example, aqueous or oilysuspensions, solutions emulsions, syrups or elixirs, or may be presentedas a dry product for constitution with water or other suitable vehiclebefore use. Such liquid preparations may contain conventional additivessuch as suspending agents, for example, sorbitol syrup, methylcellulose, glucose/sugar syrup, gelatin, hydroxyethylcellulose,carboxymethyl cellulose, aluminium stearate gel or hydrogenated ediblefats; emulsifying agents, for example, lecithin, sorbitan mono-oleate oracacia; non-aqueous vehicles (which may include edible oils), forexample, almond oil, fractionated coconut oil, oily esters, propyleneglycol or ethyl alcohol; solubilizers such as surfactants for examplepolysorbates or other agents such as cyclodextrins; and preservatives,for example, methyl or propyl p-hydroxybenzoates or ascorbic acid. Thecompositions may also be formulated as suppositories, e.g. containingconventional suppository bases such as cocoa butter or other glycerides.

For buccal administration the composition may take the form of tabletsor lozenges formulated in conventional manner.

The composition according to the invention may be formulated forparenteral administration by injection or continuous infusion.Formulations for injection may be presented in unit dose form inampoules, or in multi-dose containers with an added preservative. Thecompositions may take such forms as suspensions, solutions, or emulsionsin oily or aqueous vehicles, and may contain formulatory agents such assuspending, stabilising and/or dispersing agents. Alternatively theactive ingredient may be in powder form for constitution with a suitablevehicle, e.g. sterile, pyrogen-free water, before use.

The compositions according to the invention may contain between 0.1-99%of the active ingredient, conveniently from 1-50% for tablets andcapsules and 3-50% for liquid preparations.

The advantageous pharmacokinetic profile of the compounds of theinvention is readily demonstrated using conventional procedures formeasuring the pharmacokinetic properties of biologically activecompounds.

Compounds of formula (1) may be prepared by reaction of the carboxylicacid (11, wherein R₁, R₂ and R₃ have the meanings defined in formula 1).

or an activated derivative thereof with the amine NHR₄R₅ wherein NR₄R₅has the meaning defined in formula (1) under standard conditions forpreparing amides from a carboxylic acid or a mixed anhydride thereof andan amine HNR₄R₅.

Thus the amide of formula (1) may be prepared by treating the carboxylicacid of formula (11) with an activating agent such as BOP(benzotriazol-1-yloxy-tris(dimethylamino)phosphoniumhexafluorophosphate), TBTU(2-(1H-benzotriazol-1-yl)-1,1,3,3-tetramethyluronium tetrafluoroborate),BOP-Cl (bis(2-oxo-3-oxazolidinyl)phosphinic chloride) or oxalyl chloridein an aprotic solvent such as dichloromethane optionally in the presenceof a tertiary amine such as triethylamine and subsequent reaction of theproduct thus formed with the amine NHR₄R₅.

Alternatively the amide of formula (1) may be prepared by reacting amixed anhydride derived from the carboxylic acid (11) with the amineNHR₄R₅ in an aprotic solvent such as tetrahydrofuran. Conveniently thereaction is carried out at low temperatures e.g. approximately −78 C.The mixed anhydride is conveniently prepared by reacting the carboxylicacid (11) with a suitable acid chloride e.g. pivavolyl chloride in anaprotic solvent such as ethyl acetate in the presence of a tertiaryorganic base such as a trialkylamine e.g. triethylamineand at lowtemperatures e.g. approximately −78 C.

Compounds of formula (1) may also be prepared by reacting a compound offormula (111)

(wherein R₁R₂ and R₃ have the meanings defined in formula (1) and R₆ is2-hydroxy phenyl) with carbonyl dimidazole or thiocarbonyl diimidazolein a suitable solvent such as dichloromethane and subsequent reaction ofthe products this formed with the amine HNR₄R₅.

Compounds of formula (11) may be prepared from a compound of formula(111) wherein R₆ is 2-hydroxyphenyl by reaction with carbonyldiimidazoleor thiocarbonyidiimidazole in a suitable solvent such as dichloromethaneand subsequent reaction of the product thus formed with aqueous acetone.

Compounds of formula (111) wherein R₆ is 2-hydroxphenyl may be from thecorresponding compounds of formula (111) wherein R₆ is a2-benyloxyphenyl group by hydrogenolysis using hydrogen and a palladiumcatalyst.

Compounds of formula (111) wherein R₆ is a 2-benyloxyphenyl group areconveniently prepared by the process described herein below. Thuscompounds of formula (III) may be prepared from the compound of formula(IV)

wherein R₁, R₂ and R₃have the meanings defined in formula (I), R₇ is2-benzyloxyphenyl and R₈ is N-benzyloxycarbonyl by the reaction withhydrogen in the presence of a palladium on charcoal catalyst and aceticacid. This reaction is conveniently carried out in a solvent such asethanol or trifluoroethanol or mixtures thereof.

The compound of formula (IV) may be prepared by reacting the amino esterhydrochloride (V), wherein R₂ has the meaning defined and formula (I)

with the aldehyde R₃CHO (VI) wherein R₃ has the meanings defined informula (I), in the presence of triethylamine and in a solvent such astrifluoroethanol and then reacting of the resultant product with thecompound (VII) wherein R₁ has the meanings defined in formula (I) and R₇is a benzyloxycarbonyl

and the isocyanide CNR₆ (VII) wherein R₆ is a 2-benzyloxyphenyl group,in a solvent such as trifluoroethanol.

The R₂ substituent is a 1-methylpropyl group and the compound of formula(I) wherein R₂ is a 1-methylpropyl group having an (S) or (R)configuration may be prepared by starting with the aminoester (V)wherein the R₂ group has the required (S) or (R) configuration.

The following examples are illustrative, but not limiting of theembodiments of the present invention.

General Purification and Analytical Methods

Analytical HPLC was conducted on a Supelcosil LCABZ+PLUS column (3.3cm×4.6 mm ID), eluting with 0.1% HCO₂H and 0.01 M ammonium acetate inwater (solvent A), and 0.05% HCO₂H 5% water in acetonitrile (solvent B),using the following elution gradient 0-0.7 minutes 0% B, 0.7-4.2 minutes0%-100% B, 4.2-5.3 minutes 100% B, 5.3-5.5 minutes 0% B at a flow rateof 3 ml/minute. The mass spectra (MS) were recorded on a Fisons VGPlafform spectrometer using electrospray positive [(ES+ve to give MH⁺and M(NH₄)⁺ molecular ions] or electrospray negative [(ES-ve to give(M-H)⁻ molecular ion] modes on a Micromass series 2 or a Waters ZQ massspectrometer. ¹H NMR spectra were recorded using a Bruker DPX 400 MHzspectrometer using tetramethylsilane as the external standard. Biotage™chromatography refers to purification carried out using equipment soldby Dyax Corporation (either the Flash 40i or Flash 150i) and cartridgespre-packed with KPSil. Mass directed autoprep refers to methods wherethe material was purified by high performance liquid chromatography on aHPLCABZ+5 μm column (5 cm×10 mm i.d.) with 0.1% HCO₂H in water and 95%MeCN, 5% water (0.5% HCO₂H) utilising gradient elution at a flow rate of8 ml minutes⁻¹. The Gilson 202-fraction collector was triggered by a VGPlafform Mass Spectrometer on detecting the mass of interest.

Hydrophobic frits refer to filtration tubes sold by Whatman. SPE (solidphase extraction) refers to the use of cartridges sold by InternationalSorbent Technology Ltd. TLC (thin layer chromatography) refers to theuse of TLC plates sold by Merck coated with silica gel 60 F₂₅₄. Oasis™refers to Waters® Oasis™ HLB Extraction Cartridges, sold by WatersCorporation®.

INTERMEDIATE 12-{(3R,6R)-3-(2,3-dihydro-1H-inden-2-yl)-6-[(1S)-1-methylpropyl]-2,5-dioxo-1-piperazinyl}-N-(2-hydroxyphenyl)-2-(2-methyl-1,3-oxazol-4-yl)acetamide

To a vigourously stirred solution of (D)-allo Isoleucine methyl esterhydrochloride (5.0 g) in dichloromethane (150 ml) was added a saturatedsodium bicarbonate solution (150 ml). The resultant bi-layer wasseparated using a hydrophobic frit and the aqueous phase washed twicewith dichloromethane (50 ml). The combined dichloromethane phase wasdiluted with methanol (200 ml) and(2R)-[(benzyloxycarbonyl)amino](2,3-dihydro-1H-inden-2-yl)ethanoic acid(14.64 g) added and the mixture vigorously stirred for 1 hr to effectsolution. The solution was evaporated and the residue dissolved in amixture of 1:1 trifluoroethanol/methanol (140 ml), and then2-benzyloxyphenylisocynanide (9.43 g) was added followed by2-methyl-4-formyloxazole (5.0 g) and the reaction stirred for 4 days atroom temperature. The mixture was evaporated and the residue dissolvedin ethanol (500 ml) and palladium on carbon (4.0 g) and acetic acid (10ml) added and the reaction mixture was stirred under an atmosphere ofhydrogen for 3 hours. Further fresh palladium on carbon (4.0 g) andacetic acid (20 ml) added and the reaction mixture was stirred under anatmosphere of hydrogen for a further 16 hours. The mixture was filteredthrough Celite, evaporated and the residue dissolved in ethyl acetate(300 ml) washed with water (2×100 ml), saturated sodium bicarbonatesolution (2×100 ml) and brine (100 ml) and then passed through ahydrophobic frit and evaporated. The crude product was purified bycolumn chromatography (silica) eluting with ethyl acetate(100% to 0%):methanol to give2-{(3R,6R)-3-(2,3-dihydro-1H-inden-2-yl)-6-[(1S)-1-methylpropyl]-2,5-dioxo-1-piperazinyl}-N-(2-hydroxyphenyl)-2-(2-methyl-1,3-oxazol-4-yl)acetamide(11.8 g 51 %)

HPLC Rt=3.2 minutes; m/z [M+H]⁺=517.

Similarly prepared from (D)-isoleucine methyl ester hydrochloride

INTERMEDIATE 22-{(3R,6R)-3-(2,3-dihydro-1H-inden-2-yl)-6-[(1R)-1-methylpropyl]-2,5-dioxo-1-piperazinyl}-N-(2-hydroxyphenyl)-2-(2-methyl-1,3-oxazol-4-yl)acetamide

HPLC Rt=3.17 and 3.22 minutes; m/z [M+H]⁺=517.

INTERMEDIATE 3{(3R,6R)-3-(2,3-dihydro-1H-inden-2-yl)-6-[(1S)-1-methylpropyl]-2,5-dioxo-1-piperazinyl}(2-methyl-1,3-oxazol-4-yl)aceticacid

Carbonyldiimidazole (352 mg, 1.6 equiv.) was added to a solution of2-{(3R,6R)-3-(2,3-dihydro-1H-inden-2-yl)-6-[(1S)-1-methylpropyl]-2,5-dioxo-1-piperazinyl}-N-(2-hydroxyphenyl)-2-(2-methyl-1,3-oxazol-4-yl)acetamide(11.8 g pre-dried in vacuo over P₄O₁₀ for 24 hours) in dichloromethane(20 mL) and the solution was left at room temperature for 16 hr. Themixture was evaporated and the residue dissolved in acetone (20 ml) andwater (20 ml) added, followed by addition of 2NHCl (2 ml) and themixture left at room temperature for 4.5 hr. This was extracted withethylacetate (2×30 ml) and the combined organic phase dried via ahydrophobic frit and evaporated. The residue was taken up inethylacetate (30 ml) washed with 2NHCl (2×10 ml) and then extracted withsaturated sodium bicarbonate solution (2×15 ml). The combined aqueousphase was acidifed with 2NHCl and extracted with ethylacetate (2×20 ml)and the combined organic phase washed with brine dried via a hydrophobicfrit and evaporated to give{(3R,6R)-3-(2,3-dihydro-1H-inden-2-yl)-6-[(1S)-1-methylpropyl]-2,5-dioxo-1-piperazinyl}(2-methyl-1,3-oxazol-4-yl)aceticacid (0,355 mg, 73%) as a white solid.

HPLC Rt=3.0 and 3.1 minutes; m/z [M+H]⁺=426

Similarly prepared from intermediate 2

{(3R,6R)-3-(2,3-dihydro-1H-inden-2-yl)-6-[(1R)-1-methylpropyl]-2,5-dioxo-1-piperazinyl}(2-methyl-1,3-oxazol-4-yl)aceticacid (Intermediate 4)

HPLC Rt=3.14 minutes; m/z [M+H]⁺=426

EXAMPLE 1(3R,6R)-3-(2,3-dihydro-1H-inden-2-yl)-1-[(1R)-1-(2-methyl-1,3-oxazol-4-yl)-2-(4-morpholinyl)-2-oxoethyl]-6-[(1S)-1-methylpropyl]-2,5-piperazinedione;m/z [M+H]⁺=495

¹HNMR (CD Cl₃) δ 7.72 (s, 1H), 7.26-7.15 (m, 4H), 6.93 (d, 1H), 6.30 (s,1H), 4.18 (d, 1H), 4.06 (dd, 1H), 3.70-3.30 (m, 8H), 3.17-3.10 (m, 3H),2.98-2.86 (m, 1H), 2.81-2.75 (m, 1H), 2.49 (s, 3H), 1.69-1.60 (m, 1H),1.50-1.43 (m, 1H), 1.05-0.95 (m, 1H), 0.80-0.75 (m, 6H).

Similarly was prepared from intermediate 4 and morpholine

EXAMPLE 2(3R,6R)-3-(2,3-dihydro-1H-inden-2-yl)-1-[(1R)-1-(2-methyl-1,3-oxazol-4-yl)-2-(4-morpholinyl)-2-oxoethyl]-6-[(1R)-1-methylpropyl]-2,5-piperazinedione

HPLC Rt=2.92 minutes; m/z [M+H]⁺=495

EXAMPLE 3(3R,6R)-3-(2,3-dihydro-1H-inden-2-yl)-1-[(1R)-1-(2-methyl-1,3-oxazol-4-yl)-2-(4-morpholinyl)-2-oxoethyl]-6-[(1S)-1-methylpropyl]-2.5-piperazinedione

(2R)-[(benzyloxycarbonyl)amino](2,3-dihydro-1H-inden-2-yl)ethanoic acid(35.84 g, 0.110 mol) in a 500 mL round bottomed flask was treated with2,2,2-trifluoroethanol (165 mL) followed by methanol (55 ml) andtriethylamine (11.13 g, 15.33 mL, 0.110 mmol) the slurry was stirred for3.5 hrs until dissolution was observed. The solution was then added to(D)-allo Isoleucine methyl ester hydrochloride (20 g, 0.110 mol) in aseparate flask. The slurry was stirred until dissolution was observed.2-methyl-4-formyloxazole (12.24 g, 0.110 mmol) was then added followedby 2-benzyloxyphenylisocynanide (23.04 g, 0.110 mmol). The dark brownreaction mixture was then stirred at 20-25° C. for 24 hrs. The solutionwas then concentrated to a volume of ca. 130 mL by distillation atreduced pressure. The solution was the diluted with dichloromethane (200mL) and washed with water (2×200 mL). The organic phase was then dilutedwith N-methyl pyrrolidinone (460 mL) was and the dichloromethane removedby stirring at 40° C. under vacuum for 2 hrs. Acetic acid 46 mL) wasthen added followed by palladium on carbon catalyst (69.0 g of 10% Pdwt, 57% water, Johnson Matthey type 87L) and the mixture hydrogenatedunder balloon pressure of hydrogen with rapid stirring for 2 hrs. Thereaction mixture was then filtered, washed through with ethyl acetate(960 mL) and washed with 3% w/v aq sodium chloride solution (960 mL).The biphasic mixture was filtered and the organic phase separated andwashed with 3% w/v aq sodium chloride solution (2×960 mL). The organicsolution was then diluted with ethyl acetate (200 mL) and concentratedby distillation at atmospheric pressure by distilling out 385 mL ofsolvent. The concentrated solution at 20-25° C. was treated with1,1′-carbonyidiimidazole (21.46 g, 0.132 mol) and stirred at 20-25° C.for 1 hr then treated with water (290 mL) and stirred rapidly at 20-25°C. for 24 hr. The mixture was allowed to settle and the ethyl acetatelayer separated and discarded. The aqueous phase was washed with ethylacetate (290 mL) and the mixture allowed to settle and the aqueous phasewas separated and acidified to pH 1-2 by the addition of concentratedhydrochloric acid (18 mL). The aqueous phase was then extracted intoethyl acetate (290 mL and then 145 mL). The combined ethyl acetatesolution was then concentrated by distillation at atmospheric pressureto a volume of ca. 93 mL. This solution was then diluted withtetrahydrofuran (62 mL) and treated with triethylamine (11.02 g, 15.20mL, 0.109 mol) and cooled to −78° C. The solution was then treated withtrimethylacetyl chloride (4.81 g, 4.92 mL, 39.90 mmol) and stirred at−78° C. for 7 hr. The reaction mixture was then treated with a solutionof morpholine (15.82 g, 15.83 mL, 0.181 mol) in tetrahydrofuran (23 mL)and stirred at −78° C. for 1 hr 20 mins before being allowed to warm to20-25° C. The solution was then diluted with ethyl acetate (76 mL) andwashed with saturated aqueous sodium bicarbonate solution (2×153 mL)followed by water (153 mL). The organic solution was then diluted withethyl acetate (54 mL) and distilled down to a volume of 69 mL atatmospheric pressure. The solution was then cooled to 20-25° C. at whichpoint crystallisation of the title compound occurred. The slurry of wasthen cooled further to 0° C. before the title compound was isolated byfiltration and sucked dry. Yield 8.92 g.

PHARMACY EXAMPLES

These examples illustrate the preparation of a representativepharmaceutical formulations for administration containing a compound ofthe invention.

A. Parenteral Formulation

Ingredients Compound of the invention 1 g Absolute alcohol 5 mLPropylene glycol 25 mL 5% w/v 2-hydroxypropyl β cyclodextrin in 50 q.s.100 mL mM acetic acid containing 0.9% sodium chloride adjusted to pH 4.0with sodium hydroxide.

The compound of the invention is dispersed in the alcohol and dissolvedin the propylene glycol by the aid of heat. The aqueous component isthen added with stirring to provide 10 mL of the I.V. solution. Thesolution may be sterilised by appropriate means such as asepticfiltration or autoclaving.

This may be administered by bolus or diluted into an infusion bagcontaining, for example normal saline.

B. Capsule for Oral Administration.

Ingredients % wt./wt. Compound of the invention 25.0 Lactose 74.5Magnesium stearate 0.5

The above ingredients are mixed and dispensed into hard gelatin capsulescontaining 100 mg each.

C. Tablet for Oral Administration.

Ingredients % wt./wt. Compound of the invention 25.0 Lactose 35.0 Starch34.5 Crospovidone 4.0 Magnesium stearate 0.5

The above ingredients with the exception of the magnesium stearate arecombined and mixed. The magnesium stearate is then added and theformulation mixed. The formulation is formed into tablets with anappropriate tableting machine.

Measurement of Oxytocin Antagonist Activity

Assay Buffer used throughout the assay: 50 mM HEPES, 10 mM MgCl2, 0.125mg/ml BSA, pH adjusted to 7.4 with KOH. hOT-CHO membranes were preparedat a concentration of 0.3 mg protein/ml in assay buffer. Test compoundswere initially dissolved in DMSO (to 10 mM) and diluted in DMSO (BeckmanBiomek FX). 1 μl of compound was transferred to black 384 assay plates(NUNC) using a Biomek FX. 20 μl of 1 nM Bodipy TMR Oxytocin (PerkinElmer) in assay buffer was added to all wells (Labsystems Multidrop)then 20 μl membrane added to all wells (Multidrop). Plates wereincubated at room temp for 60 min.

Polarisation was read on LJL Analyst (λEx=535 nm, λEm=580 nM,λDichroic=555 nm). Data were filted to a 4 parameter logistic equation.An estimated Ki was calculated as IC50/5.

In the above test compounds of examples 1 and 2 of the invention have apKi value of 9.0 and 8.2 respectively.

The compounds of the invention are essentially non toxic attherapeutically active doses. Thus compound of the example 1 has beenadministered to rats at doses of 30 mg/kg for 7 days and no adversetoxicological effects were observed.

1. A compound which is(3R,6R)-3-(2,3-dihydro-1H-inden-2-yl)-1-[(1R)-1-(2-methyl-1,3-oxazol-4-yl)-2-(4-morpholinyl)-2-oxoethyl]-6-[(1S)-1-methylpropyl]-2,5-piperazinedione.2. A pharmaceutical composition comprising a compound as claimed inclaim 1 together with one or more pharmaceutically acceptable carriers.